If the hair, skin, and fatty pads were removed from the vulva, several underlying structures could be seen. If you look at Figure 3.2, which shows the structures underneath the labia and clitoris beneath the hood, you are looking at a complex of structures with erectile tissue that engorges with blood during sexual arousal, causing the vulva to swell and creating increased erotic sensations. You can see that the glans is connected to the shaft. The shaft contains two small spongy structures called the cavernous bodies. The clitoral shaft expands into the large spongy erectile tissue of the crura that connect to the pubic bones in the pelvic cavity. The vestibular (veh-STIB-yoo-ler) bulbs lie under the inner labia and extend from below the clitoris to surround the urethral and vaginal openings (O’Connell, 2007). The urethra is also surrounded by erectile tissue, called the urethral sponge. Underneath the skin between the opening of the vagina and the anus, a dense network of blood vessels, the perineal sponge, fills with blood and also becomes more sensitive to touch and pressure (Chalker, 2002). Compression of the engorged complex of erectile tissues by insertion of fingers, sex toys, or the penis into the vagina causes internal sensations that some women find pleasurable (Ellison, 2000).
Bartholin’s glands, one on each side of the vaginal opening, typically produce a drop or two of fluid just before orgasm. The glands are usually not noticeable, but sometimes the duct from a Bartholin’s gland becomes clogged, and the fluid that is normally secreted remains inside and causes enlargement. If this occurs and the swelling does not subside within a few days, it is best to see a health-care practitioner.
Besides the glands and network of vessels, a complex musculature underlies the genital area, as seen in I Figure 3.3. The pelvic floor muscles have a multidirectional design that allows the vaginal opening to expand greatly during childbirth and to contract afterward.